1. Field of the Invention
This invention relates generally to pressurized dispensing containers, and more particularly, to a system and method for providing a reserve supply of gas in a pressurized container, and especially to a system and method for storing gases adsorbed or absorbed on a sorbent material such as, e.g., activated carbon, zeolite, or molecular sieves, in pressurized containers, and subsequently releasing the sorbed material in response to a decrease in pressure below a predetermined level in the container. In one aspect, the reserve supply of gas is used to restore and maintain propellant pressure as the dispensed product and/or propellant are depleted from a pressurized dispensing container, to thereby improve the useful service life of the system. In another aspect, the invention relates to the replenishment of a carbonization gas in a carbonated beverage, or to the addition of a supplement, e.g., oxygen, to a beverage. The invention also relates to a process for filling and/or pressurizing such containers.
2. Prior Art
Pressurized containers are commonly used to dispense many products, including paint, lubricants, cleaning products, food items, personal care products such as hair spray, and the like. These containers include systems in which the product and propellant are stored separately in a container, i.e., separated by a barrier, e.g. a piston or bag, commonly referred as a barrier pack system, and systems in which the product and a suitable propellant are stored together under pressure in the container. Dispensing of the product occurs when a discharge valve or nozzle is opened, permitting the pressurized product to be forced out through the nozzle, usually as a spray, stream, or foam. As product is depleted from the container, the pressure exerted by the propellant decreases, especially evident when compressed gases are used as the propellant, and the propellant pressure may become diminished to the extent that all of the product cannot be dispensed from the container, or desired characteristics, e.g., atomization, are not achieved.
In addition to the propellant component, many products, e.g., hair spray, require a carrier, e.g., alcohol, or combinations of alcohol with water or other volatile solvents that dry quickly upon discharge from the container. Other volatile solvents that can be used in these systems include volatile organic compounds (VOCs) such as propane, isobutane, dimethyl ether, and the like, but their use is limited due to environmental concerns. For instance, under some current regulations no more than 55% of the contents of the container can comprise a VOC. In an aerosol dispenser, as much as 25% of the VOC could be required for use as a propellant, leaving about 30% VOC in the product. The balance of the product would be the active ingredient and water, which does not dry as quickly as the VOC, resulting in a “wet” product when used.
Carbon dioxide (CO2) is environmentally friendly, and is therefore useful as an aerosol propellant, but its use has been limited due to the fact that it is normally placed in the container as a pressurized or compressed gas, and the drop-off in pressure is excessive as the product is used. For example, in a typical situation the starting pressure might be 100 psig and the finishing pressure only 30 psig. At this low finishing pressure all of the product may not be discharged, and/or proper atomization may not be achieved.
Other systems relying upon gas pressure to discharge a product include cans of pressurized gas that are intended for use in cleaning dust and the like from sensitive equipment, such as computers, computer keyboards, etc., by blowing a pressurized stream of the gas onto the equipment. Using compressed carbon dioxide as the gas in these systems is not entirely satisfactory because of the rapid fall-off in pressure as the gas is used. Accordingly, other gases, such as fluorocarbon (e.g., Dymel® by DuPont), are sometimes used in these systems. However, these materials are relatively expensive for the intended use.
Conventional barrier pack systems typically comprise acan made of aluminum, steel, plastic, or other suitable material, with a barrier in the can between the product and the propellant. The barrier normally comprises a piston reciprocable in the can, or a collapsible bag in which the product is contained. Empty cans, either with a piston in place in the can, or a bag attached to the valve or dome closing the end of the can, are commonly shipped from the can manufacturer to a location where the can is to be filled.
If the barrier pack is of the type having a piston, the filler normally introduces product, e.g., a gel, into the can above the piston. The aerosol valve is then fitted and sealed to the can, and a liquefied propellant such as, e.g., isobutene, a VOC, is introduced under a predetermined pressure into the can beneath the piston through a sealing plug in the bottom of the can. Some of the liquefied propellant vaporizes until an equilibrium pressure is reached. The pressurizing propellant forces the piston up, placing pressure on the product so that it is discharged through the valve when the valve is opened. The amount of pressure available from the liquefied propellant is finite, and as product is depleted and the pressure drops, suitable atomization or discharge of the product may not be achieved, especially after most of the product has been discharged.
In those barrier packs utilizing a bag, the filler introduces product into the bag, and then introduces a liquefied propellant into the can around, or outside, the bag. The propellant exerts pressure on the bag, forcing product out through the valve when the valve is opened. As discussed above, suitable atomization or discharge of the product may not be achieved as product is depleted and the pressure decreases.
Other pressurized systems include carbonated beverages, and over time the carbonization decreases, resulting in a “flat” drink Various systems have been developed in the prior art for adding propellant to a container as product is depleted, so that propellant pressure is maintained at a desirable level until a suitable amount of the product is dispensed from the container. Other systems have been developed for introducing or replenishing a propellant or carbonization gas in a carbonated beverage. Exemplary of such prior art systems are those disclosed in the following US Patents: U.S. Pat. No. 3,858,764 (issued to Wilkinson Sword Ltd); U.S. Pat. No. 4,049,158 (to S.C. Johnson & Sons, Inc.); U.S. Pat. No. 4,182,688 (to The Drackett Company); U.S. Pat. No. 4,518,103 and U.S. Pat. No. 6,708,844 (to Walter K. Lim and Arthur A. Krause); U.S. Pat. No. 5,032,619 and U.S. Pat. No. 5,301,851 (to Rocep-Lusol Holdings Ltd.); U.S. Pat. No. 5,256,400 (to Advanced Polymer Systems, Inc.); U.S. Pat. No. 5,562,235 (to Rudiger Cruysberghs); U.S. Pat. Nos. 6,390,923 and 6,745,922 (to Heineken Technical Services BV); 6,527,150 (to L'Oreal SA); and 6,770,118 (to World Laboratory Complex).
U.S. Pat. No. 3,858,764 discloses a pressurized dispenser in which a reservoir formed of an organic substance (e.g., rubber) holds supplemental propellant in solution. The patent states at lines 38-44, column 4, that the material must be capable of holding the propellant in solution, as opposed to merely absorbing propellant into the pores or interstitial spaces of the material.
U.S. Pat. No. 4,049,158 discloses the placement in a pressurized container of a quantity of gas adsorbent material, e.g., activated carbon, having a quantity of gas, e.g., CO2, adsorbed thereon as a reserve supply of pressurized gas to maintain a desired pressure in the container. The patent discloses several embodiments, including a barrier pack (piston or bag), and a non-barrier pack (pouch or envelope). The adsorbent material is placed in a separate pressure source chamber that can have a fixed volume and communicate with the product chamber via a check valve or a constant pressure valve, or the source chamber can be expandable, or the source chamber can be a pouch or envelope containing the adsorbent material. The adsorbent material is, in all cases, in a pressure source chamber separate from the product chamber that prevents contact between the adsorbent material and the product.
U.S. Pat. No. 4,182,688 discloses a gas-adsorbent propellant system that is intended for use to clear waste stoppages in a conduit, and essentially fills a container with adsorbent material (e.g., activated carbon) on which CO2 is stored for subsequent release when the discharge valve is opened. The system is designed so that a large quantity of the gas itself is available for several discharges of one second duration at a pressure of about 30 psig.
U.S. Pat. No. 4,518,103 discloses a method and apparatus for releasing additional propellant into a pressurized container, wherein a reserve container in the primary container holds a quantity of liquefied propellant and is constructed to open or rupture as a result of a predetermined reduction in the pressure in the primary chamber, to thereby release additional propellant into the primary container. The release of additional propellant occurs essentially all at once when a predetermined pressure differential is reached.
U.S. Pat. No. 5,032,619 describes a system for storing and dispensing gas, but discloses that the stored gas can be used as a propellant. It relies upon non-rigid swellable polymers, such as, e.g., hydrogels (although zeolite is also mentioned), having microvoids in which the gas is stored. The patent describes several embodiments, including: (1) a two-phase gas/solid system in which gas is stored in the microvoids of the solid polymer; (2) a three-phase gas/liquid/solid system in which a liquid solvent of the gas occupies the microvoids (preferred solvents are identified as water and other “polar solvents”); (3) a two-phase gas/liquid system in which the gas is dissolved in a liquid solvent for the gas (examples given include CO2 dissolved in acetone); (4) a pressure pack having a gas storage system according to (1), (2) or (3) above; and (5) a procedure for pressurizing a barrier-type pressure pack dispenser as described in (4) above, wherein a quantity of polymeric material (and solvent if used) are placed in a container on the side of the barrier opposite that of the product, followed by the addition of a non-gaseous form of the propellant gas (e.g., dry ice), and then sealing the container. In all cases, a barrier separates the polymer from the product (the barrier may comprise a piston or a bag, or an envelope containing the polymeric material). It is disclosed that the product could be inserted prior to or after the propellant. The “polar solvent” is disclosed as being added to promote swelling of the polymer.
U.S. Pat. No. 5,256,400 discloses a pressurized product delivery system in which a gas is sorbed in the macropores of a polymeric matrix having a pore size of from about 0.0001 μm to about 3.0 μm. The preferred polymeric material is said to be a copolymer of methyl methacrylate and ethylene glycol dimethacrylate, with the polymeric particles having a porosity of at least 30%, and preferably greater. The polymeric material is disclosed as being compressed into pellets or tablets, and the gas is described as being stored in macropores of the sorbent material. Many different possible polymers and monomers are listed, but no mention is made of activated carbon, zeolite or molecular sieve materials. The patent mentions that the product, polymer and propellant can all be in the same chamber, and in those systems a screen, filter, or the like, can be included to prevent plugging of the valve and nozzle (implying that the sorbent material will be in small particle form).
U.S. Pat. No. 5,562,235 discloses a system in which reserve propellant gas is stored under pressure in a separate pressure source chamber in the product-containing chamber, and a pressure operated valve controls flow of the reserve gas from the pressure source chamber into the product chamber. There is no suggestion of adsorption of gas onto a gas-adsorbing media.
U.S. Pat. No. 6,390,923 discloses a system for dispensing carbonated beverages, e.g., beer, in which a source of pressurized gas, e.g., CO2, is contained in a separate compartment with pressure control means to control its release into the product chamber and maintain equilibrium pressure. The patent states that the process can be used for dispensing other products, but does not disclose how or what.
U.S. Pat. No. 6,527,150 discloses a system for packaging a product, particularly a cosmetic, wherein a reserve pressure source chamber is received in a translucent or transparent outer product container, and the product and pressure source chambers are separated from one another in a sealed manner. A liquefied propellant is in the pressure source chamber, and a “retainer” in that chamber traps the liquid phase of the propellant. At least one portion of the retainer is permeable to the gas phase. It is disclosed that the propellant can be a hydrocarbon, and the retainer may be an open cell foam, felt, or porous membrane, or sintered metal or silicone, located spaced from the container bottom.
U.S. Pat. No. 6,708,844 discloses a system in which a quantity of adsorbent material, e.g., activated carbon, has a quantity of gas, e.g., CO2, stored thereon and is placed in a product chamber for release of the stored gas into the product as the pressure in the product chamber is depleted. The system can be used as a propellant for discharging the product, or as a source of carbonation to maintain carbonation in a carbonated beverage, or to add a supplement to a beverage. The adsorbent material may formed into a cohesive shape such as a ball or cube and placed directly in the product, or the adsorbent material may be encased in a cover that can be impermeable or permeable to the product.
U.S. Pat. No. 6,770,118 discloses a gas storage capsule and method for filling it, wherein the capsule is intended to be placed in a container holding a product to pressurize the product. Charcoal, zeolite, silica gel, or their mixtures can be placed in the capsule as a sorbent for a gas such as CO2, Ar, N2, O2, etc.
Some of these prior art systems are relatively complex and expensive, relying upon mechanical valves or other pressure responsive devices to release the stored reserve propellant. In some cases the reserve propellant is dissolved in a solvent and stored as a liquid, while in other cases the reserve propellant is stored as a gas on a gas adsorbent material. However, a substantial amount (typically 50%) of the stored gas is not released and remains on the storage material. The efficiency of these systems is thus reduced and in order to obtain release of a desired amount of reserve propellant, excess storage material and/or propellant must be placed in the container. This then adds to the cost and inefficiency of the system.
It would be desirable to have an economical, efficient, and environmentally safe system and method for providing a reserve supply of gas in a pressurized container. In particular, it would be desirable to have a system and method for providing a reserve supply of gas to restore and maintain propellant pressure as product is depleted from a container, wherein the gas is adsorbed on a gas adsorbent material and means is provided to promote release of all or substantially all of the stored gas.